Defrost indicator



E. M. GAUL DEFROST INDICATOR July 6, 1954 2 Sheets-Sheet 1 Filed Nov. 24. 1950 iazaafd 'aal July 6, 1954 GAUL 2,682,856

DEFROST INDICATOR Filed Nov. 24, 1950 2 Sheets-Sheet 2 fiz/e nforx ZUwaraQ/Z. aul

Patented July 6, 1954 n DEFROST INDICATOR Edward M. Gaul, Evansville, Ind., assignor to International Harvester Company, a corporation of New Jersey Application November 24, 1950, Serial No. 197,379

7 Claims. 1

This invention relates generally to a defrost indicator and more particularly to a defrost indicator for the cooling element of a refrigeration system.

In a refrigeration system where air to be cooled is passed over the cooling element, moisture usually condenses from the air onto the surface of the cooling element and collects and freezes thereon in the form of ice or frost. In order that the refrigeration system will operate properly and efficiently, this frost formation must be removed from the cooling element before it becomes too thick. This must be done periodically and is usually accomplished by manually setting the temperature control to defrost position.

In many refrigeration systems, it is difficult for the operator to judge the thickness of the frost formation. This is particularly true of the modern domestic refrigerator equipped with a horizontal evaporator in which the exterior surfaces of the evaporator cannot be seem by the.

operator.

It is therefore an object of this invention to provide the cooling element of a refrigeration system with a defrost indicator.

Another object of the invention is to provide a defrost indicator which is accurately responsive to the thickness of the frost-formation on the cooling element of a refrigeration system.

A further object of the invention is to provide a defrost indicator which is secured on a cooling element in such a position that it can be easily seen by the operator.

A still further object of the invention is to provide a defrost indicator which is simple, inexpensive, and easily assembled on the cooling unit of a refrigeration system.

These and other objects will become apparent from the following description taken in conjunction with the accompanying drawings, in which preferred embodiments are illustrated. .Other forms of the invention embodying the same or equivalent principles may be used and structural changes may be made as desired by those skilled in the art without departing from the present invention and the scope of the appended claims.

In the drawings:

Il ig. 1 is a front elevational View of the top portion of a refrigerator cabinet embodying the present invention.

Fig. 2 is an enlarged sectional view of a portion of the evaporator taken on line 2-2 of Fig. 1.

Fig. 3 is a front elevational view of aportion of the evaporator with the defrost indicator attached thereto. y

Fig. 4 is a sectional view taken on line 44 of Fig. 1.

Fig. 5 is an enlarged sectional View of a portion of the evaporator with a modified defrost indicator attached thereto.

Fig. 6 is a front elevational view of a portion of the evaporator with the modified defrost indicator attached thereto.

Fig. '7 is a view similar to Fig. 5 except that the evaporator door is open.

Referring to the drawings for a detailed description of the invention, numeral 19 generally indicates a refrigerator having a decorative or outer shell I I with an inner liner l2 spaced therein. Insulation material [3 fills the space between the outer shell I l and inner liner 1 2 and a breaker strip l4 bridges across this space around the periphery of a door opening. A door 15 is secured to outer shell II by hinges 16. The inner liner I2 forms a storage compartment II in which food to be refrigerated is placed.

In the upperportion of the storage compartment l l, a horizontal evaporator I8 is positioned. The evaporator is constructed from sheet metal with side walls [9 and 20, back wall 2 l and bottom wall 22 which enclose a fast freezing compartment 23.. The evaporator is provided with corrugations or passageways 24 through which refrigerant is circulated. A drip tray 25 is positioned below the evaporator l8 and mounted on brackets 25. The bottom of the drip tray 25 is filled with insulation in order to reduce the amount of heat transfer from the evaporator 8 to the storage compartment H. The refrigerant cools the evaporator I8 as it circulates through passageways 24 and thus maintains the fast freezing compartment 23 at a low temperature. The side edges 21 and 28 and back edge 29 of drip tray 25 are spaced inwardly from the walls of inner liner l2 which allows a limited amount of air to circulate therethrough. The walls of the evaporator [8 are also spaced inwardly from the walls of the inner liner 2. The air which circulates upwardly from storage compartment ll is cooled when it contacts the walls of the evaporator, and in this manner the temperature of the food storage compartment [1 is maintained at a predetermined temperature.

Since it is not desirable for air to circulate from the front part of the evaporator it, an evaporator door 30 is pivotally mounted on a horizontally disposed rod 3|. The door comprises an outer door pan 32, inner door pan 33 and insulation 34 therebetween. To open the door 30, it is pivoted about rod 3| and access is provided into the fast freezing compartment 23. A vertically disposed baffle 35 having an inturned flange 36 is secured to side wall In of the evaporator it by rivets 31. This bafiie prevents the cold air between side wall i9 and the inner liner l2 from spilling out around the evaporator door 36. A second vertically disposed baflie 33 having an inturned flange 39 is secured'to side wall 29 of the evaporator 18 by rivets 31. This bafiie prevents the cold air between side wall 29 and the inner liner 12 from spilling out around the evaporator door 353.

As the air from food storage compartment H and fast freezing compartment 23 is circulated over the cold surfaces of the evaporator [3, its temperature will be lowered and some of the moisture in the air will be condensed on the walls of the evaporator. This condensate will freeze on the evaporator and frost formation will have started. Since the exterior walls of the evaporator IB are blocked from view by baffles 35 and 38, it is necessary to provide some means for indicating when defrosting is required. The present invention provides a defrost indicator li positioned on the side wall [9 of the evaporator. A slot 52 is provided in baffle 35 through which the operator can view the defrost indicator.

l'he defrost indicator ii comprises a U-shap'ed wire spring having legs 43 and id connected by curve-:1 portion is. The end 56 of leg s4 is offset and is secured to the evaporator if in any suitable manner, such as welding. Leg 33, curved portion it and leg 4 are located in a common plane parall l to and slightly spaced from the wall 59 of evaporator 18. The indicator in its free position is slightly tilted with a portion of leg d3 extending through the lower portion of slot 42. The end 5? of leg 53 is curved back toward leg A4 in order to provide a curved surface adjacent the evaporator door. As seen in Fig. 2, when the evaporator door 3b is open, the defrost indicator ii will assume its free position with approximately one third of leg 33 projecting through slot d2. As the door is closed, the end Q7 of leg it will be contacted by the door and be pushed inwardly and upwardly to the position indicated by the dotted lines in Fig. 2. With the evaporator door closed, leg it will be deflected so that it does not extend beyond baiiie strip 35.

When very little frost or ice has accumulated on the evaporator l8 and the door is opened, the defrost indicator will spring back to its free position with leg d3; projecting through the slot 32 whereby it is visible to the operator. This indicatesthat the evaporator does not need defrosting. As the frost formation continues to grow on the evaporator .i 8, it will eventually reach a thickness great enough to contact the defrost indicator ii. When the evaporator door l t is opened, the defrost indicator will not spring to its free position since it will be frozen to or embedded in the frost. Therefore, leg Q3 will not project through slot 52 which indicates that the evaporator needs defrosting.

In the modified form of the invention shown in Figs. 5, 6 and '7, a defrost indicator 48 is pivoted of evaporator [8 in any suitable manner. The heat conductivity properties of pin 49 are low so that the temperature of defrost indicator 48 will not be lowered by the transfer of heat through pin 49 to evaporator l8. Pin 49 is provided with annular shoulders 51 and 58 which are positioned on each side of projections 56 and serve to position the defrost indicator in spaced relationship to side wall I9.

When the evaporator door 36 is opened, the defrost indicator 48 is free to rotate on the pin 49 and its center of gravity is such in respect to pin 49 that it will assume a free position with straight edge 53 in a plane inclined approximately as seen in Fig. '7. In this position the projection and the lower portion of the defrost indicator projects through slot 42 in baffle 35 and is visible to the operator. As the evaporator door is closed, it will contact projection and rotate the defrost indicator until both projections 54 and 55 are contacting the door and straight edge 53 is disposed in a vertical plane as shown in Fig. 5. As long as the evaporator 53 does not need defrosting, the defrost indicator 55 will rotate on pin 49 when the door it is opened and the lower portion will project through slot 42. When the layer of frost on the evaporator i8 has accumulated to the place that the outer surface thereof contacts the defrost indicator A8, the defrost indicator will not rotate to its free position when the evaporator door fill is opened since it will be frozen to or embedded in the frost. Therefore, the lower portion will not project through slot 42 which indicates that the evaporator needs defrosting.

From a consideration of the above description, it is seen that the invention provides means whereby an operator can easily detect if the evaporator of a refrigerator needs defrosting merely by opening the evaporator door and glancing at the defrost indicator. Since the evaprator door of a household refrigerator is usually opened several times a day for the purpose of placing food in the fast freezing compartment or removing food therefrom, the operator will be immediately aware that defrosting is needed when the defrost indicator does not protrude through the slot 42 in bafile 35. Both embodiments of the defrost indicator described above are simple in structure and will accurately signal when defrosting is required.

Although the invention has been described with respect to preferred embodiments thereof, it is to be understood that it is not to be so limited since changes can be made therein which are within the full intended scope of this invention as de lined by the appended claims.

Ihat is claimed is:

1. A refrigerator comprising an evaporator, a U-shaped resilient member having a first leg and a second leg connected by a curved portion, the end of said first leg attached to said evaporator, a door pivotally mounted which contacts said second leg and deflects said resilient member when in closed position, said resilient member returning to its free position when the door is in open position, said resilient member arranged so that it will be embedded in frost and held in its deflected position when the evaporator needs defrosting.

2. A refrigerator comprising an evaporator, a U-shaped spring having a first leg and a second leg connected by a curved portion, the end of said first leg attached to said evaporator, means for engaging said second leg and deflecting the spring, said means adapted to be moved out of engagement with said second leg so that said spring returns to its free position, said spring arranged in spaced relationship to said evaporator so that when the evaporator needs defrosting the spring will be partially embedded in frost and be prevented from returning to its free position.

3. A refrigerator comprising an evaporator, a pin having one end secured to said evaporator, a semi-circular shaped plate having an off-center portion pivotally secured'to the other end of said pin in spaced relationship to said evaporator, and

a pivotally mounted evaporator door, said plate having a lower portion which extends outwardly when the door is open, said door contacting said lower portion when closed which rotates said plate and forces said lower portion inwardly, said plate rotating back with said lower portion extending outwardly when the door is opened if the evaporator does not need defrosting, said plate being held with said lower portion extending inwardly when frost formation has accumulated on said evaporator and contacted said plate which indicates that said evaporator needs defrosting.

4. In combination, a refrigerator evaporator upon which frost will collect during normal operation, a fulcrum member mounted to one vertical wall and adjacent to the front face of said evaporator, an element formed to lie substantially in one plane, said element mounted to be deflectable about said fulcrum member with the plane of said element positioned parallel to said one vertical wall and a distance therefrom substantially equal to the normal thickness of frost forming thereon at which defrosting of said evaporator is required, so that said element is rendered completely undefiectable by said normal thickness of frost forming upon said vertical wall, said element further formed to include means for deflecting a portion of said element beyond said front face, and manually operable means for enabling said last mentioned means. 5. In combination, a refrigerator evaporator upon which frost will collect during normal operation, a fulcrum member mounted to one vertical wall and adjacent to the front face of said evaporator, an element formed to lie substantially in one plane, said element mounted to be deflectable about said fulcrum member with the plane of said element positioned parallel to said one vertical wall and a distance therefrom substantially equal to the normal thickness of frost forming thereon at which defrosting of said evaporator is required, so that said element is rendered completely undeflectable by'said normal thickness of frost forming upon said vertical wall, said element further formed to include means for deflecting a portion of said element beyond said front face, and an evaporator door pivotally mounted to said front face and engaging said element in the closed position and enabling said last mentioned means in the open position.

6. In combination, a refrigerator evaporator upon which frost will collect *during normal operation, a fulcrum member mounted to one vertical wall and adjacent to the front face of said evaporator, an element formed in the shape of a U lying substantially in one plane, one endof said element mounted to said fulcrum member with the plane of said element positioned parallel to said one vertical wall and a distance therefrom substantially equal to the normal thickness of frost forming thereon at which defrosting of said evaporator is required, so that said element is rendered completely undefiectable by said normal thickness of frost forming upon said vertical wall, said element further formed of a resilient material and biased to project a portion of said element beyond said front face, and an evaporator door pivotally mounted to said front face engaging said element in the closed position to overcome said bias and enabling said bias to project a portion of said element beyond said front face in the open position.

7. In combination, a refrigerator evaporator upon which frost will collect during normal operation, a fulcrum member mounted to one vertical wall and adjacent to the front face of said evaporator, an element formed in the shape of a plate lying substantially in one plane, said element mounted to be deflectable about said fulcrum member with the plane of said element positioned parallel to said one vertical wall and a distance therefrom substantially equal to the normal thickness of frost forming thereon at which defrosting of said evaporator is required, so that said element is rendered completely undeflectable by said normal thickness of frost forming upon said vertical wall, said element further formed in a shape such that one end thereof is deflected beyond said front face when the center of gravity thereof is positioned beneath the portion thereof which is mounted to said fulcrum member, and an evaporator door pivotally mounted to said front face and engaging said element to maintain said one end thereof substantially rearward of said front face in the closed position and enabling said one end of said element to be deflected beyond said front face in the open position.

References Cited in the file of this patent UNITED STATES PATENTS Date Number Name 1,945,100 Troll Jan. 30, 1934 1,999,191 I-Iirschl Apr. 30, 1935 2,007,409 Schweitzer July 9, 1935 2,064,396 Volpin Dec. 15, 1936 2,081,128 Volpin May 18, 1937 2,095,102 Philipp Oct. 5, 1937 2,112,261 Backstrom Mar. 29, 1938 2,571,787 Tobey 1 Oct. 16, 1951 

